1. Technical Field
The present application relates to a method and apparatus for measuring the concentration of a test substance in an organism.
2. Description of the Related Art
The concentration of a test substance (such as glucose) contained in an organism is measured, according to a known method, based on the light that has irradiated the organism and has been reflected or scattered from, or transmitted through, the organism. For example, a method for calculating the concentration of a test substance based on the radiant intensity of Raman scattered light that has been observed in the test substance is being developed.
Japanese Patent No. 5002078 (which will be hereinafter referred to as “Patent Document 1”) discloses a technique for measuring highly accurately the concentration of a biogenic component such as glucose in an interstitial fluid. According to the technique, a fine particle chip including metallic nanoparticles is embedded in the dermis of an organism and is irradiated with substantially parallel light coming from outside of the organism. Then, the light produced on the fine particle chip is detected.
WO 2002/030275 (which will be hereinafter referred to as “Patent Document 2”) and WO 2005/110207 (which will be hereinafter referred to as “Patent Document 3”) also disclose methods for measuring the glucose concentration. According to those methods, first of all, fine particles including a reagent, of which the fluorescence property changes in reaction to glucose, are embedded in an upper layer of the skin. Next, those fine particles are irradiated with light having an excitation wavelength coming from outside of the organism, and the fluorescent light produced by the fine particles is measured percutaneously. Based on the fluorescent light measured, the glucose concentration is measured.
WO 2006/111929 discloses a method for measuring the spatial concentration gradient of a biogenic component outside of a blood vessel by irradiating a volume surrounding the blood vessel in an organism with excitation light and by detecting the light produced in the volume.
Furthermore, WO 2001/001852 (which will be hereinafter referred to as “Patent Document 4”) discloses a method of detecting light produced inside an organism by irradiating the organism with light coming from outside of the organism. According to the method disclosed in Patent Document No. 4, even if the concentration of a biogenic component changes steeply, the accuracy of measuring the concentration of the biogenic component can still be maintained. According to Patent Document 4, the accuracy of measurement is maintained by establishing an equilibrium at an accelerated rate between the respective concentrations of biogenic components inside and outside of the blood vessel by heating the organism or using any other appropriate means.